Modern distribution cabinets cannot be compared with those that were installed in Soviet times. Shields in old houses are generally a problem area for electricians of service companies. There is no question of any protection of home networks, rather the opposite. The state of most of them is truly dangerous. And the point here is not even the lack of automation, but the methods of wiring. The absence of grounding and neutral tires in the shields leads to fires and other emergencies. It is worth looking into why this is happening.
What is a zero bus and why is it needed
This is the name of the brass plate with terminals, which is attached inside the switch cabinet. It serves to distribute zero across apartment lighting groups and power lines. Currently, the rules for the installation of electrical installations (PUE) provide forobligatory installation of a zero bus in the shield in order to ensure the absence of its breaks throughout. With good contact on the bar, protection against reverse heating is achieved.
Everyone who once dismantled an old outlet noticed burning of the insulation on one wire in the absence of similar signs on the other. Any experienced electrician, having barely looked at this, will say that the blackened contact is zero, and he will be absolutely right. It is on him that the main load falls, which is much higher in the power cabinet. It is to prevent such situations that a zero tire in the shield is required.
Rules for installing and connecting a contact strip
A similar terminal block can be installed in any easily accessible place in the power cabinet. The connection of the zero bus in the shield is as follows. An incoming zero is applied to the fixed bar. The contact is tightly fixed. After that, all neutral wires that go to the apartment groups are clamped into the terminals. From the zero bus, they go directly to the premises or to residual current devices (RCDs) or differential current circuit breakers (RCBOs).
It is important that the bar is firmly fixed. Otherwise, it will not be possible to stretch the zero contacts qualitatively, which will lead to an increase in temperature at the junction. In this case, only one loosely fixed contact will lead to heating of the entire bar, which will lead to weakening of the remaining connections.
Zero installation ordertires in flap
If a new distribution cabinet is being installed, this work is easier to do. It is more difficult if you have to upgrade an old assembly. In this case, installers often encounter aluminum wires, which are highly oxidized, resulting in loose contacts.
Fixing the zero bus in the shield is carried out at the stage of the location of the protective automation, even before it is connected. Switching is performed simultaneously with AV, RCD, AVDT and an electricity meter. To do this, an incoming zero is pulled from the introductory two-pole machine, after which they start wiring from the bus in groups.
What is the difference between neutral and ground busbars
RCD or RCBO for protection today are widely used. It is for their correct operation that grounding is required, which must be distributed in the same way as zero. It is for this that the same bar with terminals is used. In the absence of a contour, you can do the following. The zero bus in the shield is combined with the ground, after which separate wires go from each of them.
The main thing is that after the RCD or RCBO they do not touch. Otherwise, correct operation is out of the question. This action is called protective nulling. It cannot be called a full-fledged grounding, but it copes with its task.
Benefits of installing a zero bar in the switch cabinet
Not everyone understands the importance of such installation, believing that if it is necessary in the shieldcombine only 3-4 cores, this can be done using ordinary twisting. This can be answered that it is enough to have such switching under a good load, and after 20-30 minutes the insulation will begin to warm up, after which it will flare up. It is worth analyzing what advantages the installation of a zero tire in the shield gives:
- Presence of multiple points to which neutral wires can be connected.
- Providing easy access for serviceability when inspecting electrical power cabinets.
- Improving the efficiency of the elements of protective automation due to the absence of heating.
Some tips for maintaining zero tires
Like any other power cabinet equipment, such a bar requires constant attention. After putting the shield into operation, after 1-2 weeks, the connections should be stretched again. The fact is that the oxide film that forms on the surface of the core will burn by this time, which will lead to a weakening of the connection.
At least 2 times a year, this procedure must be repeated, as in the case of protective automation. It is necessary to ensure that dust does not accumulate on the zero bus. Ideally, if it is closed with a plastic transparent lid. You should sometimes check the bar visually - a bad contact will give itself away as a darkening of the busbar or wire insulation near the connection.
Summarizing the above
Don't underestimate the importance of mounting zerotires, content with twists or bolted connections. Such a bar is an element of protection that complements automation, allowing it to work correctly and do what it is mounted for, namely, to ensure the safety of electrical wiring.
